Our objective was to determine in children in the intensive care unit (ICU) the incidence of hyperchloremia (>110mmol/L) and hypochloremia (<98mmol/L), the association of diagnoses with chloride abnormalities, and the associations of mortality and acute kidney injury (AKI) with chloride abnormalities. We analyzed the initial, maximum, and minimum chloride measurements of 14,684 children in the ICU with >= 1 chloride measurement in the Health Facts database between 2009 and 2016. For hyperchloremia and hypochloremia compared with normochloremia, mortality rates increased three to fivefold and AKI rates increased 1.5 to threefold. The highest mortality rate (7.7%; n=95/1,234) occurred with hyperchloremia in the minimum chloride measurement group and the highest AKI rate (7.7%; n=72/930) occurred with hypochloremia in the initial chloride measurement group. The most common diagnostic categories associated with chloride abnormalities were injury and poisoning; respiratory; central nervous system; infectious and parasitic diseases; and endocrine, nutritional, metabolic, and immunity disorders. Controlled for race, gender, age, and diagnostic categories, mortality odds ratios, and AKI odds ratios were significantly higher for hyperchloremia and hypochloremia compared with normochloremia. In conclusion, hyperchloremia and hypochloremia are independently associated with mortality and AKI in children in the ICU.